This invention relates to a novel parts sensing device and method for use in conjunction with the operation of parts forming equipment in sensing the presence and/or absence of newly formed parts.
Parts forming equipment, various types of which utilize methods including injection molding, die casting, stamping and deep-drawing or forging press, has in recent years become increasingly automated. This equipment usually operates with a cyclical procedure, repeating the same set of operations each time a part or set of parts is formed. Working cosely with or as a part of the parts forming equipment there is usually engaged an extractor apparatus which has some means of gripping the newly formed parts, removing them from the mold, die or other similar tooling of the parts forming equipment and depositing the parts with whatever means will continue the parts preparation or packaging operation. Although some parts forming equipment is designed to eject the newly formed parts without a distinct extractor apparatus, in all cases it is imperative in order to prevent damage to the dies, molds or other similar tooling of the parts forming equipment that all newly formed parts be completely removed from the molds or dies before the next cycle in the parts forming operation begins. Inasmuch as an increasing proportion of the parts forming equipment in use is automated (without human operators), the safe and economical operation of the equipment calls for the implementation of a sensing device which, also working automatically, can accurately monitor the removal of the newly formed parts from the molds or dies.
Sensing devices for parts forming equipment are still in the early stages of development. The most commonly used methods incorporate air or vacuum sensing systems into the parts extractor apparatus used with the parts forming equipment. The sensing systems are coupled with suction cups that "grip" the parts to be removed. This type of system, however, is subject to several significant drawbacks. First, these systems are limited in the number of parts, especially small parts, that can be sensed. Secondly, the systems require the use and maintenance of air and vacuum systems. Further, with the reciprocating action and movement of the robot extractors and the vibration which accompanies such movement, leaks almost inevitably occur in the system. Owing to the nature of the system the leaks are very difficult to locate. And too, the vacuum system, although having the capacity to sense that all parts have been picked up by the extractor does not have the capacity to sense that each part has been released from the extractor means.
Another method is the application of an optoelectric system using fibre-optic sensors which are attached to the extractor apparatus of the parts forming equipment. These systems, too, have proven to be unsatisfactory. The many movements and degrees of freedom of motion in the extractor robots lead to frequent failures in the systems. The delicate fibre-optics are unable to withstand the almost incessant flexing, vibration and shock movements of the robotic arms and early failures of the fibre-optic sensors occur. Moreover, the fibre-optic sensors for such uses are relatively expensive to replace.
A third method of sensing newly formed parts in conjunction with parts forming equipment is through the use of television cameras. In such a system, a television camera is used to scan the mold or die of the parts forming apparatus, the camera signal is then read to determine whether parts are still present in the mold or die. If a part is "stuck" in the mold or die an appropriate "stop" signal is sent to the parts forming apparatus. In addition to being an expensive method of sensing (from the standpoint of high initial investment), this system is subject to other disadvantages as well. The television camera must be mounted at some position outside the immediate area of the mold or die and it views the mold base or die at an angle. The television camera field of view thereby limits the size or shape of the mold base that can be used and therefore the number of parts that can be sensed. This is remedied only by the economically undesirable and space demanding option of incorporating additional television cameras and control mechanisms. Furthermore, such systems are relatively inflexible due to the fact that to change the number, location or shape of the parts being detected may require not only repositioning of the camera but reprogramming the means which reads the camera signal so that it "detects" the new arrangement of parts.
None of the parts sensing methods in current use has proven to be a satisfactory solution to the multi-dimensional needs of the parts forming industries.
Accordingly, it is an object of the present invention to provide a relatively inexpensive yet highly reliable parts sensing device for sensing the presence and/or absence of parts in conjunction with the operation of parts forming equipment.
Another object of the present invention is to provide a parts sensing device which monitors the presence and/or absence of a relatively large number of parts, makes a determinaton that all parts have been sensed as present or absent and communicates signals representing these determinations to either an indicator means or the controller of the parts forming equipment.
Another object of the present invention is to provide a parts sensing device which uses logic circuits to make its determinations that all parts have been sensed as present or absent.
It is yet another object of the present invention to provide a parts sensing device which can make the above described determinations even when a portion of its potential sensor sites are not in use.
Still another object of the present invention is to provide a parts sensing device which, when used in conjunction with extractor apparatus, can sense not only when all parts have been "gripped" by the extractor apparatus, but also when the parts have been successfully released by the extractor apparatus.
Still another object of the present invention is to provide a parts sensing device which utilizes individual parts sensors which are relatively inexpensive and can be easily and quickly removed and replaced.
Another object of the present invention is to provide a parts sensing device which is highly flexible in that the number and location of its individual sensor means can be quickly, easily and inexpensively altered to accommodate the special needs of parts forming industries such as the injection molding industry where the size and shape as well as the number of parts formed at each parts forming cycle are frequently changed.
It is yet another object of the present invention to provide a parts sensing device which provides a parts present or absent indicator for each sensor site as well as indicators to show whether all sensors are "on" or all sensors are "off".
Another object of the present invention is to provide a parts sensing device having an indicator means by which defective sensors can be identified.
It is yet another object of the present invention to provide a parts sensing device which requires only a relatively small number of connecting means from a control means to a display means and yet still has the capacity to provide at the display means an indicator for each sensor to show whether that sensor is "on" or "off".